Europe ‘faces invasion from tropical viruses’

Diseases such as West Nile fever, yellow fever, dengue fever and Japanese encephalitis mostly occur in the tropics and other warm regions of the world.

But they are already becoming more widespread thanks to the greater movement of people, goods and animals.

Writing in The Lancet medical journal today, experts said it was likely global warming would accelerate the spread of these viruses into southern and even northern Europe.

The invaders belong to a family of “flaviviruses” that are transmitted by blood-sucking insects.

One of them, the yellow fever virus, causes up to 200,000 infections and 30,000 deaths in sub-Saharan Africa each year.

There is no vaccine available against dengue virus, which can produce dangerous fevers and cause the body to go into shock. Both these viruses are carried by the mosquito Aedes aegypti.

Authors Dr Ernest Gould, from the Centre for Ecology and Hydrology in Oxford, and Professor Tom Solomon, from the University of Liverpool, wrote: “As Aedes aegypti disperses more widely we might… witness dengue virus emerging in warmer regions of Europe and North America.”

Increasing numbers of epidemics due to flaviviruses such as West Nile virus could be expected in southern Europe and perhaps even northern Europe, they argued.

They said: “Warmth and humidity favour increased densities of ticks, and there is accumulating evidence that east Asian strains of tick-borne encephalitis are now circulating in central and west-central Europe, possibly introduced to the warmer and wetter regions via ticks carried by migrant birds.”

All these viruses were well defined but “unpredictable” said the experts.